Positron tomograpy is emerging now as a powerful tool for clinical diagnostics. In essence it involves a radiative scanning device coupled with positron emitting radioactive sources that are introduced into specific organs or tissues. The positrons decay by the emission of two gamma rays in diametrically opposed directions, and the scanning of those gamma pairs allows a detailed and accurate three dimensional mapping of the area of interest to be performed.
Typical sources employed in positron tomography have to be isotopes of materials that can easily be introduced into biological molecules. The most commonly employed materials .sup.11 C with a half life of 20.5 min and .sup.18 F with half life of 110 min. The short lifetimes of these sources provide added advantages: the patients are not exposed to excessive radiation and the safety precautions in handling these materials can be simple, since accidental spills will not produce any lasting contamination. The short lifetimes of the positron sources have, however, another important consequence: the sources have to be produced in the immediate vicinity of their eventual use and since those positron sources can be produced only with the air of particle accelerators, this implies having suitable accelerators established on hospital sites. The proper running of a positron tomography facility requires the adaptation of the accelerator operation, the source production, the radio chemistry and the scanning to hospital practices and norms.